This invention relates to a mechanical lock, and in particular, to a sidebar for preventing forced rotation of the lock cylinder.
A mechanical key lock includes a cylinder rotatably supported within a sleeve. In order to prevent rotation of the cylinder without a mated key, a sidebar is utilized. When the mated key is inserted in the cylinder, the key and the cylinder may be rotated within the sleeve.
The sidebar is placed within a slot in the cylinder and within an aligned groove in the sleeve in order to prevent the cylinder from being rotated relative to the sleeve. The sidebar is biased away from the sleeve toward the interior of the cylinder by springs. Tumblers, supported within the cylinder, maintain a portion of the sidebar within the groove in the sleeve when the mated key is not present in the cylinder.
Each tumbler includes a notched portion having reduced diameter. When the mated key is inserted in the cylinder, the notches on each tumbler align with the sidebar. As a result, the biased sidebar is urged towards the notches in the tumblers by action of the springs. If the tumblers have been properly set by the mated key, the sidebar will enter the notches in the tumblers and exit the groove in the sleeve. As a result, the cylinder is free to be rotated within the sleeve.
While present day sidebars are adequate, it is desirable to increase the shear strength of the portion of the sidebar within the groove in the sleeve. Increased shear strength makes forced rotation of the cylinder without a mated key more difficult. This, in turn, increases the lock's resistance to tampering.
In addition, it has been found that the tool steel for diecasting projections on the sidebar is prone to failure. The projections extend from the sidebar and are provided for receipt of the springs. Due to these projections on the sidebar, the tool steel will have a very thin section, which tends to wear easily and fail, thereby increasing downtime and maintenance costs.
Therefore, it is a primary object and feature of the present invention to provide a sidebar having increased shear strength in the portion of the sidebar which engages the sleeve of the mechanical key lock.
It is a further object and feature of the present invention to provide a sidebar which may be diecast by a tool which is stronger and less prone to failure.